1. Field of the Invention
The present invention relates to a thermoelectric material. More particularly, it relates to a P-type thermoelectric material comprising iron disilicide which can produce a large electric power, and which exhibits a small mean resistivity.
2. Description of Related Art
In Japanese Examined Patent Publication (KOKOKU) No. 60-43,881, discloses a P-type thermoelectric material which can produce a large amount of electric power. The P-type thermoelectric material comprises iron disilicide, which contains manganese (Mn), in atomic % (hereinafter % means atomic % unless otherwise specified), in an amount of from 0.5 to less than 1.67%, and aluminum (Al), wherein the combined amount of manganese and aluminum is from 2.0 to less than 4.7% in total. This patent application was issued as registered Japanese Patent No. 1,599,140.
When the P-type thermoelectric material, disclosed in Japanese Examined Patent Publication (KOKOKU) No. 60-43,881 and comprised of the iron disilicide, contains, in atomic %, Mn in an amount of 0.6%, Al in an amount of 2.7% and accordingly Mn and Al in an amount of 3.3% in total, it produces a thermoelectromotive Force of 183 mV and exhibits a mean resistivity of 0.009 ohm-cm under a temperature difference of 800.degree. C. Consequently, the P-type thermoelectric material can produce an effective maximum power of 0.96 Wcm/cm.sup.2.
The P-type thermoelectric material is usually used together with an N-type thermoelectric material as a pair. The N-type thermoelectric material used together with the P-type thermoelectric material as a pair, for instance, an iron disilicide N-type thermoelectric material exhibits a mean resistivity of 0.0053 ohm-cm under a temperature difference of 800.degree. C. The resistivity is smaller by a 41.1% than that of P-type thermoelectric material comprised of iron disilicide. Accordingly, the electric power produced by the iron disilicide N-type thermoelectric material is larger than the electric power produced by the P-type thermoelectric material comprised of iron disilicide. However, the N-type thermoelectric material and the P-type thermoelectric material are normally used in a pair as a unit. Consequently, the original mean resistivity of the unit as a whole is larger than the inherent resistivity of the iron disilicide N-type thermoelectric material. As a result, the inherent high capacity of the iron disilicide N-type thermoelectric material is canceled, and thereby there arises a problem that the inherent high capacity cannot be fully utilized.